Cathode ray image projecting device



Feb. 25, 1941. H. SMITH CATHODE RAY IMAGE PROJECTING DEVICE Filed Aug'.29, 1940 2 Sheets-Sheetv 1 INVENTOR Patented Feb. 25, 1941 UNITED STATESPATENT oEFlcE 18 Claims.

This inventionr relates to improvements in systems for the reception ofpicture scanning signals. The improvements. proposed are particularlyconcerned with the system of projecting a light .5- image from a cathoderay scanning device described in my previous application No. 299,611.The cathode ray image projecting device covered in my previousapplication includes a vibratory horizontal image forming surface uponwhich is deposited an electric image by the scanning beam. A layer ofopaqe image forming particles on the image forming surface becomesionized when the image surface is vibrated and the particles areagitated, resulting in their distribution on the surface in accordancewith the electric image deposited by the scanning beam. Since theelectric image charges deposited by the scanning beam must remainlargely undissipated through each interval of vibration and agitatingthe image forming particles, a means of charging or ionizing the imageforming particles which is separate from the scanning beam is desirable.Where the electric image charges are deposited on one surface, say thelower side of a horizontal vibratory plate and the opaque image formingparticles are distributed on another parallel surface, say the upperside of this same plate, some method of uniformly charging the layer ofopaque particles during agitation is required.

'Ihe present invention is concerned with improved methods of ionizingthe image forming particles and accomplishing the formation of asemi-opaque image corresponding to the electric image.

In accordance with one modification of my invention, ionization of theimage forming particles is accomplished by applying by means of anelectrode necessary positive or negative electrical potential to .theimage surface which is sufciently conducting so that either a deficiencyor an excess of negative charges exists throughout the surface and onthe image particles. Since the image surface and the image formingparticles thereon are charged alike, both positive, or both negative, arepulsive electrostatic force exists, and when the surface vbrates andthe particles rebound from the surface, they will remain in a charged orionized state and will be susceptible to electrostatic repulsion orattractential resulting from the charges of the electric image depositedby the scanning beam. This will be described in detail in connectionwith the drawings.

In accordance with another modification of my tion by the image surfacepoints of higher poinvention, the image forming particles may be chargedthrough electrostatic induction wherein electric charges existing on aseparate plane surface parallel to the image forming surface induce apreponderance of positive or negative 5 charges on the image formingsurface and on the image forming opaque particles in contact with thesurface. This electric charge or ionization is retained by the imageforming particles as they rebound from the surface. If an electricpotential is used to produce the charges on the separate plane surface,one side of that potential may be connected directly to an electrodeassociated with the image forming surface. No appreciable flow ofcurrent would occur, however, since the charges on the particles arereturned again to the image forming surface on the next rebound.

To accomplish uniform ionization of the image. forming particles withoutthe. use of excessive electrical potential applied to the image surface,

I may make use of light sensitive material in the image formingparticles. This material may be either of the photoelectric or surfaceemission .type or of the photovoltaic or potential generating type.

The electric image which is deposited by the scanning beam in the devicemay be on the vibrating image forming surface itself` or on anotherparallel surface in close proximity thereto. This will be apparent fromthe alternative arrangements shown in the drawings.

Referring to the drawings, Fig. l shows a preferred arrangement of atelevision receiving system With cathode ray image projecting device inwhich the electric image surface and the semiopaque image formingsurface are one and the same.

Fig. 2 shows a plan view of a section of the image forming surface usedin the device of Fig. l.

Fig. 3 is a graph of the probable distribution for a short timeinterval, of the electric potential along a straight line path on aportion of the image forming surface of Fig. 1, and represents the pointto point summation of the potentials due to both the uniform surfacecharge and the electric image charges deposited by the scanning beam.

, Fig. 4 shows a modified construction using one surface for theelectric image which is deposited by the scanning beam and anothersurface on which is formed the semi-opaque image.

Fig. 5 showsv another arrangement of electric image and semi-opaqueimage forming surfaces in which the light is reflect-ed by the imageforming surface instead of being transmitted through it.

Fig. 6 shows another modification with the electric image deposited onone side of a vibratory plate with the image forming particles on theopposite side.

Fig. 7 shows a preferred construction of a small projection tube whichcan be vibrated as a whole to agitate the opaque particles on the imageforming surface in the tube.

Fig. 8 shows a modified arrangement with a vibratory plate in the tubeactuated through a flexible joint in the tube wall by an externalwinding and magnetic core.

Fig. 9 is a sectional view along line A-A in Fig. 8. I

Fig. 10 shows a preferred arrangement in which the image formingparticles are charged through electrostatic inductive action employingla plane surface electrode parallel to the image surface.

In Fig. 1 the scanning signals are received on some form of receivingelement I which may be a Wire circuit or a radio antenna. After passingthrough the receiving amplifier 2, the image signals which willdetermine the light and shadow effects in the light image to bepro-duced are then connected to the cathode ray image reproducing tube 3through the conductors 4 which are connected to the cathode 5 and thecontrol grid 6. The output of the receiving amplifier 2 is alsoconnected to the input of the scanning deflection signal amplifier 1.Amplifier 'l separates the high and low frequency scanning deflectionsignals which are transmitted separately to the ampliners 8 and 9 havingsuitable characteristics for the respective deflection signals.

With the high frequency deflection signals from the output of amplifier8 connected to the electrodes Ill and the low frequency deflectionsignals from amplifier 9 connected to the coils I I, the requireddeflecting fields are set up which cause the cathode beam I2 to scan thesurface of diaphragm I3 in synchronism with the scanning operation atthe transmitting end of the circuit.

The low frequency scanning deflection signals from selective amplifier'I are also connected to amplifier I4 whose output is connected to thesynchronous motor device I5 used to drive the light interrupting disk I6and commutator and slip ring arrangements Il and lil. In this manner theinterrupting disk I6 and commutators I'I and I8 are rotated insynchronism with the low frequency scanning deflection signal. Theshaded and unshaded segments of the commutators Il and I8 arepermanently connected to the respective shaded and unshaded slip rings.

Diaphragm I3 may be formed of resilient glass material and is fused atthe edge to the flange of the glass tube 3. The flange of diaphragm I3is provided with holesv which receive the bolts 39 holding togethercemented joints between the diaphragm I3 and iron core 2I and betweenthe iron core 2| and the glass cover `33. 'Ihe spaces above and belowthe diaphragm I3 are evacuated and the diaphragm I3 is entirely free tovibrate due to its flexible design. The top surface of diaphragm I3 hasa ring shaped electrode 29 with a connection brought out through theflange of the tube 3. The ring 29 and its connection is of silver platedonto the diaphragm surface. The diaphragm I3 has a thin layer 32 ofsmall particles of opaque ceramic insulating material on its top surfaceinside of the ring 29. The vibration of diaphragm I3 is controlled bythe coil I9 which is mounted on porcelain insulating sleeves 34 on thestiff wire supports 35. The upper ends of the wires 35 are sealed intothe diaphragm I3. Coil I9 carries an alternating current from source 29during the scanning operation.

The iron core 2I, shown in section, extends completey around theperiphery of the tube 3 and is magnetized by the direct current winding22 also shown in. section. The iron magnetic shields 39 and 3l alsoextend completely around the p-eriphery of the tube and serve to shieldthe center portion of the diaphragm I3 from stray magnetic flux. Theshield 36 is provided With slots through which pass the coil supports35.

The cathodel ray tube 3 is also provided with the usual acceleratingelectrode 23 and auxiliary electrode 25 for focusing the cathode beam.The accelerating potential for the electronic beam is sup-plied to anode23 through the lter 39 and commutator and slip ring arrangement I1mounted on the same shaft with the disk IS. The brushes and contactsurfaces at I1 are so arranged that the accelerating potential to anode23 is interrupted at the same time that light is allowed to pass throughthe interrupting disk I6. The collecting ring 29 is maintained at anegative potential by the source 2B. Collecting ring 29 controls theleakage currents from the surface of diaphragm I3. The potential ofanode 24 is constant and is about 4 times the potential applied to anode23.

The commutator and slip ring arrangement I8 controls the vibration ofthe diaphragm I3, and its brushes and contact surfaces are so arrangedthat an alternating current from source 29 is supplied to the winding I9during the scanning of diaphragm I3 by the beam I2, but between scanningoperations and at the same instant that light is allowed to pass throughthe disk I6, the alternating current through the coil I9 is interruptedand the coil I9 is short circuited to dampen its motion. The lightinterrupting disk I6 is provided with holes distributed at properintervals around the periphery. By means of the optical system shownbriefly, light from the source 25 passing through the diaphragm I3 andthe tube 3 and through an opening in the disk I6 is projected onto thescreen 23 in the form of a light and shadow image.

Fig. 2 is a plan Viewof a section of the diaphragm I3 and shows how theelectrical connections to the collecting ring' 29 are brought outthrough the flange of tube 3.

The operation of the system shown in Fig. 1 is as follows: The cathodebeam I2 scans the top surface of diaphragm i3 and at the same time thebeam varies in intensity all in accordance with the scanning and imagesignals received through the receiving element I. During the scanningoperation the diaphragm I3 is vibrated bycoil I9. The image formingsurface on diaphragm I3 and the opaque ceramic particles 32 thereon areuniformly charged negatively due to the negative potential 26 impressedon electrode 29. When the opaque ceramic particles rebound from thesurface of diaphragm I3 they retain lthe charges acquired while inContact with the surface of I3, since a multiplicity of charges of likepolarity repel each other. The particles 32 while in a charged orionized state are susceptible to electrostatic repulsive forces exertedby the concentrated electric image charges deposited on diaphragm- I3 bythe cathode beam I2. After each scanning operation or cycle of the lowfrequency deflection signal, the commutator slip ring arrangement I1removes the positive potential from electrode 23 interrupting the beamI2. At the same time, the commutator slip ring arrangement I8 interruptsthe alternating current in coil I9, also short circuiting the coil andstopping the vibration of diaphragm I3. Disk I6 at the same time allowslight from source 25 to be projected onto the screen 28. Due to theelectrostatic repelling action between the electric image charges on thesurface of I3 and the charged particles 32 during the vibration ofdiaphragm I3, the distribution of these particles conforms to theelectric image which was deposited by scanning beam I 2 whichcorresponds to the light and dark portions of the light image which wasscanned at the transmitting end of the circuit. This resultingsemi-opaque image is projected upon the screen 28 bythe lightoriginating at source 25.

Fig. 3 is a graphical representation of the point to point summation ofthe electric potential along a straight line path on a portion of theimage forming surface in Fig. 1 immediately after scanning. Thepotential level I here represents the uniform surface charge accumulatedfrom clissipation of the electrical image charges and also from thesource 26. The higher potential levels 2, 3 and 4 are the result ofundissipatedelectric image charges deposited by the scanning beamvsuperimposed on the uniformly distributed charges of potential level I.The uniformly distributed charges are for the purpose of ionizing theimage forming particles as previously described.

Fig. 4 shows a partial sectional view of an image projection tube suchas 3 in Fig. 1 with a modified construction consisting essentially of aflexible flat ring 30 with two transparent plates I3 and 3| mounted inthe center. The plate I3 4 is very thin and is mounted close to thesurface of plate 3|. A scanning beam I2 deposites an electric image onthe upper surface of I3. The lower plate 3| has a layer of opaque imageforming particles 32 which may be charged by leakage currents to o rfrom an electrode 29 around the edge of plate 3|, or the particles 32may be of light sensitive self ionizing type.

Fig. 5 shows still another modified construction in which the electricimage surface I3 is stationary, while the semi-opaque image formingsurface 3| is vibrated as in Fig. 1 and Fig. 4. As a furthermodification, plate 3| is of conducting material with a polished surfaceso that a light beam such as 4I after passing through the semi-opaqueimage formed by particles 32, will be reflected in an upward directionas shown. The opaque image forming particles 32 may be ionized bycharging the surface of plate 3|, or light sensitive self ionizingparticles may be used.

Fig. 6 illustrates a modified construction for a projection tube havinga single plate I3, the under side of which is exposed to a scanning beamI2. On the upper surface of plate I3 is a thin layer of image formingparticles 32 which may be charged by leakage currents to or fromelectrode 29, or the particles may be of light sensitive self-ionizingmaterial.

Fig. 7 shows a small image projecting tube in which the image formingsurface is vibrated by vibrating the tube as a whole. The electric imagesurface I3 and image forming plate 3| are rigidly mounted in the tube.In other respects this tube functions the same as Figures 3 and 4. Itmay have a single plate functioning as an electric image surface andsemi-opaque image forming surface as in Figures l and 6 and may employan electrode such as 29 in Fig. 1 for charging the image particles 32,or may make use of light sensitive self ionizing particles.

. The modified arrangement of Fig. 8 includes a metal tube shell 3 withglass window 4 and iiexible joint 6. Image forming plate I3 is mountedin a metal ring 39 which extends through the flexible joint 6 andconnects to actuating winding I9, similar to Fig. 1. Iron core 2| andmagneticl shield 36 are similar to those inFig. 1 and also serve toconnect and reinforce the upper and lower sections of tube 3 throughbrackets 5.

In Fig.`10 the scanning beam I2 deposits an electric image on the lowersurface of vibrating screen :|3. Close to the upper surface of. thescreen I3 is a plane surface electrode 30 which may be very thin andoffer little resistance to light transmission, or it may consist of areflecting surface which reiiects the light transmitted through .theimage forming screen I3. A suitable electric potential 28 is connectedbetween the ring electrode 29 on the screen I3 and the plane surfaceelectrode 30. Potential 28 may be either a positive or a negativepotential. The potential '28 produces a preponderance of negative orpositive charges on the upper surface of screen I3 and on the opaqueimage forming par,- ticles 32, similar to the charging of the parallelplates of a condenser. The image forming particles 32 retain theyelectric charges acquired on the surface of screen I3 as they reboundfrom the surface of I3 so that they are susceptible to electrostaticaction of the electric image charges on the lower surface of screen I3resulting in their redistribution to form the desired semiopaque on thesurface of screen I3.

As an alternative arrangement to that shown in Fig. 10, I may have thetop surface of screen I3 exposed to the scanning beam and use a planesurface electrode located below the screen, or use the bottom surface ofscreen I3 as an electrode to charge inductively the top surface of thescreen I3 and the particles thereon.

In Fig. 1 I have shown a negative potential applied to the electrode 29which would impart a uniform negative charge to the image formingparticles rebounding from the surface of diaphragm I3 resulting in theseparticles being repelled from the electric image charges deposited on I3by the scanning beam I2. I may, if desired, use a positive potential on.the electrode 29 which would charge the image forming particlespositively, resulting in their being attracted by the image chargesdeposited by the scanning beam I2.

In the device shown, by way of example, in Fig. 1 I may employ imageforming particles such as 32 of photoelectric material. This eliminatesthe requirement for any excessive external potential at 26 applied totheimage forming surface with possible non-uniform effect throughout thesurface. The particles of photoelectric material would be exposed tolight from the source 25 or any auxiliary source of light of convenientwave length to sensitize the material used, and may be of the surfaceemission type, as for example cuprous oxide, or of the photovoltaic orpotential generating type, or may exhibit both phenomena. Thephotoelectric particles would become charged positively due to theaction of the light from source 25, and 'during their successiverebounds from the vibrating surface of diaphragm I3 would migratehorizontally toward the negative charges constituting the electric imagedeposited by the scanning beam I2.

It is further contemplated that the conductivity of one surface of thevibrating screen or diaphragm such as I3 in Fig. l may be controlled bythe use of thin transparent sputtered metallic lms. Such a metallic filmmight be auxiliary to a photoelectric material of the photovoltaic type,as for example, cuprous oxide particles on a thin sputtered lm ofmetallic copper.

Opaque image forming particles of photoelec` tric material may be usedwith any of the various constructions shown in Figures 1 to 10. With theexception of Fig. 10, no definite external circuit exists in which aphotoelectric current might now. Such an external circuit does exist,however, in Fig. 10 between the electrodes 29 and 30, but would noteffect the scheme of operation which is dependent only on an electronemission by a photoelectric particle, leaving the particleelectrostatically unbalanced.

Considerable variation is possible in the conductivity of the materialused for the opaque image forming particles, depending upon thearrangement of the electric image surface and the senil-opaque imageforming surface, and the density of the layer of image formingparticles. Where the electric image surface and .the semiopaque imageforming surface are one and the same, as in Fig. l, namely, the topsurface of diaphragm I3, the image particles preferably should be ofhigh electrical resistance. During vibration of the diaphragm I3 in Fig.1 and scanning of the top surface of diaphragm I3 by the beam I2, enoughrandom paths are formed by particles in contact with the surface at onetime so that too rapid dissipation of the electric image charges mig toccur if the particles were numerous enough and were of conductingmaterial. When the electric image surface and the semi-opaque imageforming surface are separated as in Fig. 6 for example, Where theelectric image charges are deposited on the lower surface of diaphragmI3 and the image forming particles 32 are on the upper surface, imageforming particles of conducting material such as carbon might be used.The exact material used would depend Vupon a number of factors, namely:conductivity of the vibrating screen surface, density of the imageforming particles, desired flow of stray currents on the screen surface,and the method of charging the image forming particles, whether from anelectrode around the edge of the screen surface, or Whether thischarging is also dependent upon an electronic scanning beam or dispersedelectronic beam covering the entire image forming surface.

This invention has been illustrated only in a general preferred formthroughout and it should be understood that it is capable of many andvaried modifications without departing from its purpose and scope, andl' therefore believe myself to be entitled to make and use any and allof these modifications such as suggest themselves to those skilled inthe art to which the invention is directed, provided that suchmodications fall fairly within the purpose and scope of the hereinafterappended claims.

What is claimed is:

1. Receiving tube comprising an electron .gun emitting an electronicbeam, a screen of transparent material of low electrical conductivityarranged so as to be exposed to the electrons emitted by the electrongun, said screen having a layer of line opaque particles on its uppersurface, means associated with the said electron gun for concentratingthe beam emitted by said electron gun and for-causing it to scan thesaid screen to deposit electric image charges thereon, means associatedwith the said receiving tube for causing said screen to vibrate in avertical direction at definite time intervals thereby agitating theopaque particles -causing said particles to rebound from the surface ofthe screen, an electrode associated with the said screen for uniformlycharging the upper surface of the screen and the opaque particles incontact with the said upper surface, whereby the said opaque particlesin rebounding from the upper surface of said screen carry away chargesfrom the said upper surface and being ionized are electrostaticallyinfluenced by the said electric image charges and are redistributed onthe upper surface of the said screen so as to form on, said screen whenit ceases to vibrate a semi-opaque image conforming to the pattern ofthe said electric image charges.

2. Receiving tube comprising an electron gun. emitting an electronicbeam, a screen of transparent material of low electrical conductivityarranged so as to be exposed to the electrons emitted by the electrongun, Lsaid screen having a layer of fine opaque particles on its uppersurface,'means associated with the said electron gun for concentratingthe beam emitted by said electron gun and for causing it to scan thesaid screen to deposit electric image charges thereon, means associatedWith said receiving tube for causing said screen to vibrate in avertical direction at definite time intervals thereby agitating theopaque particles causing said particles to rebound from the surface ofthe screen, an electrode associated with the said screen for uniformlycharging negatively the upper surface of the screen and the opaqueparticles in contact with the said upper surface, whereby the saidopaque particles in rebounding from the upper surface of said screencarry away negative charges from the said. upper surface and beingionized are electrostatically repelled by the said electric imagecharges and are redistributed on the upper surface of the said screen soas to form on the said screen when it ceases to vibrate a senilopaqueimage conforming to the pattern of the said electric image charges.

3. Receiving tube comprising an electric gun emitting an electronicbeam, a screen of transparent material of low electrical conductivityarranged so as to be exposed to the electro-ns emitted by the electrongun, said screen having a layer of fine opaque particles on its uppersurface,

means associated with the said electron gun for concentrating the beamemitted by said electron gun and for causing it to scan the said screento deposit electric image charges thereon, means associated with saidreceiving tube for causing said screen to vibrate in a verticaldirection at definite time intervals thereby agitating the opaqueparticles causing said particles to rebound from the surface of thescreen, an electrode associated with the said screen for uniformlycharging positively the upper surface of the screen and the opaqueparticles in contact with the said upper surface, whereby the saidopaque particles in rebounding from the upper surface of said screencarry away positive charges from the said upper surface and beingionized are electrostatically attracted by the said electric. imagecharges and are redistributed on the upper sur- Til face of the saidscreen so as to form on said screen when it ceases to vibrate asemi-opaque image conforming to the pattern of the said electric imagecharges.

4. Receiving tube comprising an electron gun emitting an electronicbeam, a screen of transparent material of low electrical conductivityarranged so as to be exposed to the electrons emitted by the electrongun, said screen having a layer of fine opaque particles of lightsensitive material on its upper surface, means associated with the saidelectron gun for concentrating the -beam emitted by said electron gunand for causing it to scan the said screen to deposit electric imagecharges thereon, means associated with said receiving tube for causingsaid screen to vibrate in a vertical direction at denite time intervalsthereby agitating the said opaque light sensitive particles causing saidparticles to rebound from the surface of the screen, means associatedwith the said receiving tube for uniformly lighting and energizing theopaque light sensitive particles whereby the said opaque light sensitiveparticles in rebounding from the upper surface of said screen areionized and are electrostatically attracted by the said electric imagecharges and are redistributed on the upper surface of the said screen soas to form on the said screen when it ceases to vibrate a semi-opaqueimage conforming to the pattern of the said electric image charges.

5. Receiving tube comprising an electron gun emitting an electronicbeam, a screen of transparent material of low electrical conductivityarranged so that the lower surface of said screen is exposed to theelectrons emitted by the electron gun, said screen having a layer voflfine opaque particles on its upper surface, means associated with thesaid electron gun for concentrating the beam emitted by said electrongun and for causing it to scan the lower surface of said screen todeposit electric image charges thereon, means associated with saidreceiving tube for causing said screen to vibrate in a verticaldirection at definite time intervals thereby agitating the said opaqueparticles causing said particles to rebound from the surface of thescreen, an electrode associated with the said :screen for uniformlycharging the upper surface of the screen and the opaque particles incontact with the said upper surface, whereby the said opaque particlesin rebounding from the upper surface of said screen carryv away chargesfrom the said upper surface and being ionized are electrostaticallyinfluenced by the said 'electric image charges on the lower surface ofthe said screen and are redistributed on the upper surfacel of the saidscreen so as to form on the said screen when it ceases to vibrate asemi-opaque image conforming to the pattern of the said electric imagecharges.

6. Receiving tube comprising an electron gun emitting an electronicbeam, a screen of transparent material of low electrical conductivityarranged so that the lower surface of said screen is exposed to theelectrons emitted by the electron gun, said screen having a layer of neopaque particles of light sensitive material on its upper surface, meansassociated with the said electron gun for concentrating the beam emittedby said electron gun and for causing it to scan the lower surface ofsaid screen to deposit electric image charges thereon, means associatedwith said receiving tube for causing said screen to vibrate in avertical direction at definite time intervals thereby agitating the saidopaque light sensitive particles causing said particles to re- .boundfrom the surface of the screen, means associated with the said receivingtube for uniformly lighting and energizing the opaque light ity arrangedso` as to be exposed to the electrons emitted by the electron gun, asecond screen parallel to and in close proximity to the lower surface ofsaid first screen but not exposed to the electronic beam, the saidsecond screen having on its upper surface a layer of ne opaqueparticles, means associated with the said electron gun for concentratingthe electronic beam emitted by said electron gun and for causing it toscan the upper surface of said first screen to deposit electric imagecharges thereon, means associated with said receiving tube for vibratingsaid second screen in a vertical direction at definite time intervalsthereby agitating said opaque particles causing them to rebound upwardtoward the lower surface of said first screen, means associated with thesaid receiving tube for ionizing the opaque particles on the uppersurface of said second screen, whereby the said ionized opaque particlesin rebounding from the upper surface of said second screen areelectrostatically influenced by the said electric image chargesdeposited on the said first screen so as to form on the second screenwhen it ceases to vvibrate a semi-opaque image conforming to the patternof the said electric image charges on said first screen.

-8. Receiving tube comprising an electron gun emitting an electronicbeam, a first screen of transparent material of low electricalconductivity arranged so as to be exposed to the electrons emitted bytheA electron gun, a second screen parallel to and in close proximity tothe lower surface -of said first screen butv not exposed to theelectronic beam, the said :second screen having on its upper surface alayer of fine opaque particles,` means associated with the said electrongun for concentrating the electronic beam emitted by said electron gunand for causing it to scan the upper surface of said rst screen todeposit electric image charges thereon, means associated with the saidreceiving tube for vibrating said first and second screens in a verticaldirection at definite time intervals thereby agitating said opaqueparticles causing them to rebound upward toward the lower surface ofsaid first screen, means' associated with the said receiving tube forionizing the opaque particles on the upper surface of said second screenwhereby the said ionized opaque particles in rebounding from the uppersurface of the second screen are electrostaticallyinfluenced by the saidelectric image charges deposited on the said first screen, so as to formon the second screen when it ceases to vibrate a semi-opaque imageconforming to the pattern of the said electric image charges on said rstscreen.

9'. Receiving tube comprising an electron gun emitting an electronicbeam, a 4first screen of transparent material of low electricalconductivity arranged yso as to be exposed to the electrons emitted bythe electron gun, a second screen of conducting material with a smoothreflecting surface parallel to and in close proximity to the lowersurface of said first screen but not exposed to the electronic beam, thesaid second screen having on its upper surface a layer of fine opaqueparticles, means associated with the said electron gun for concentratingthe electronic beam emitted by said electron gun and for causing it toscan the upper surface of said first screen to deposit electric imagecharges thereon, means associated with the said receiving tube forvibrating said second screen in a vertical direction at denite timeintervals thereby agitating said opaque particles causing them torebound upward toward the lower surface of said first screen, meansassociated with the said receiving tube for ionizing the opaqueparticles on the upper surface of said second screen, whereby the saidionized opaque particles in rebounding from the upper surface of thesecond screen are electrostatically influenced by the said electricimage charges deposited on the said rst screen so as to form on thereflecting surface of said second screen when it ceases to vibrate asemi-opaque image conforming to the pattern of the said electric imagecharges on said first screen.

l0. Receiving tube comprising an electron gun emitting an electronicbeam, a screen of transparent material cf low electrical conductivityarranged sc as to be exposed to the electrons emitted by the electrongun, said screen having a layer of line opaque particles on its uppersurface, means associated with the said electron gun for concentratingthe beam emitted by said electron gun and for causing it to scan thesaid screen to deposit electric image charges thereon, means associatedwith the said receiving tube for causing it to vibrate in a verticaldirection at definite time intervals thereby agitating the opaqueparticles causing the said particles to rebound from the surface of thesaid screen, an electrode associated with the said screen for uniformlycharging the upper surface of the screen and the opaque particles incontact with the said upper surface, whereby the said opaque particlesin rebounding from the upper surface of said screen carry away chargesfrom the said upper surface and being ionized are electrostaticallyinfluenced by the said electric image charges and are redistributed onthe upper surface of the said screen so as to form on the said screenwhen the receiving tube ceases to vibrate a semi-opaque image conformingto the pattern of the said electric image charges.

ll, Receiving tube comprising an electron gun emitting an electronicbeam, a screen of transparent material of low electrical conductivityarranged so as to be exposed to the electrons emitted by the electrongun, said screen having a layer of fine opaque particles of lightsensitive material on its upper surface, means associated with the saidelectron gun for concentrating the beam emitted by said electron gun andfor causing it to scan the said screen toI deposit electric imagecharges thereon, means associated with the said receiving tube forcausing it to vibrate in a vertical direction at definite time intervalsthereby agitating the opaque light sensitive particles causing the saidparticles to rebound from the surface of the said screen, meansassociated with the said receiving tube for uniformly lighting andenergizing the opaque light sensitive particles, whereby the said opaquelight sensitive particles in rebounding from the upper surface of saidscreen are ionized and are electrostatically attracted by the saidelectric image charges and are redistributed on the upper surface of thesaid screeny so as to form on the said screen when the receiving tubevceases to vibrate a semiopaque image conforming to the pattern of thesaid electric image charges.

12. Receiving tube comprising an electron gun emitting an electronicbeam, a first screen of transparent material of low electricalconductivity arranged so as to be exposed to the electrons emitted bythe electron gun, a second screen parallel to and in close proximity tothe lower surface of said first screen but not exposed to the electronicbeam, the said second screen having on its upper surface a layer of fineopaque particles, means associated with the said electron gun forconcentrating the electronic beam emitted by said electron gun and forcausing it to scan the upper surface of said first screen to depositelectric image charges thereon, means associated with said receivingtube for vibrating said tube in a vertical direction at definite timeintervals thereby agitating the opaque particles on said second screencausing them to rebound upward toward the lower surface of said rstscreen, means associated with the said receiving tube for ionizing theopaque particles on the upper surface of said second screen, whereby thesaid ionized opaque particles in rebounding from the upper surface ofsaid second screen are electrostatically influenced by the said electricimage charges deposited on the said first screen so as to form on thesecond screen when the receiving tube ceases to vibrate a semi-opaqueimage conforming to the pattern of the said electric image charges onsaid first screen.

13. Receiving tube comprising an electron gun emitting an electronicbeam, a screen of transparent material of low electrical conductivityarranged so as to be exposed to the electrons emitted by the electrongun, said screen having a layer of line particles of cuprous oxide onits upper surface, means associated with the said electron gun forconcentrating the beam emitted by said electron gun and for causing itto scan the said screen to deposit electric image charges thereon, meansassociated with the said receiving tube for causing said screen tovibrate in a vertical direction at definite time intervals therebyagitating the cuprous oxide particles causing said particles to reboundfrom the surface of the screen, means associated with the said receivingtube for uniformly lighting and energizing the cuprous oxide particleswhereby the said cuprous oxide particles in rebounding from the uppersurface of said screen are ionized and are electrostatically attractedby the said electric image charges and are redistributed on the uppersurface of the said screen so as to form on the said screen. when itceases to vibrate a semi-opaque image conforming to the pattern of thesaid electric image charges.

14. In an electronic receiving tube of the character described, avibratory image forming screen having a layer of ne opaque particles,said image forming screen being actuated by means of a mechanical linkextending through a flexible gras tight joint in the receiving tubewall, means external to the said receiving tube and connected to saidmechanical link for vibrating said image forming screen in a verticaldirection at definite time intervals.

15. Receiving tube comprising an electron gun emitting an electronicbeam, a screen of transparent material of low electrical conductivityarranged so that the lower surface of said screen is exposed to theelectrons emitted by the electron gun, said screen having a layer of neopaque particles on its upper surface, means associated with the saidelectron gun for concentrating the beam emitted by said electron gun andfor causing it to scan the lower surface of said screen to depositelectric image charges thereon, means associated with the said receivingtube for causing said screen to vibrate in a vertical direction atdefinite time intervals thereb;7 agitating the opaque particles causingsaid particles to rebound from the surface of the screen, an electrodeparallel to the upper surface of. said screen for charging byelectrostatic induction the upper surface of the screen and the opaqueparticles in `contact with the said upper surface, whereby the saidopaque particles in rebounding from the upper surface of said screencarry away induced charges from the said upper surface and being ionizedare electrostatically influenced by the said electric image charges onthe lower surface of the said screen and are redistributed on the uppersurface o-f the said screen so as to form on the said screen when itceases to vibrate a semi-opaque image conforming to the pattern of thesaid electric image charges.

i6. Receiving tube comprising an electron gun emitting an electronicbeam, a screen of transparent material of low electrical conductivityarranged so that the upper surface of said screen is exposed to theelectrons emitted by the electron gun, said screen having a layer offine opaque particles on its upper surface, means associated with thesaid electron gun for concentrating the beam emitted by said electrongun and for causing it to scan the upper surface of said screen todeposit electric image charges thereon, means associated with saidreceiving tube for causing said screen to vibrate in a verticaldirection at definite time intervals thereby agitating the opaqueparticles causing said particles to rebound from the upper surface ofsaid screen, means for uniformly charging the lower surface of saidscreen producing a uniform induced charge on the upper surface of saidscreen, whereby the said opaque particles in rebounding from the uppersurface of said screen carry away induced charges from the said uppersurface and being ionized are electrostatically iniiuenced by the saidelectric image charges on the upper surface of the said screen and areredistributed on the upper surface of the said screen so as to form onthe said screen when it ceases to vibrate a semi-opaque image conformingto the pattern of the said electric image charges.

17. Receiving tube comprising an electron gun emitting an electronicbeam, a screen of transparent material of lowv electrical conductivityarranged so that the lower surface of said screen is exposed to theelectrons emitted by the electron gun, said screen having a layer ofline opaque particles of light sensitive material on its upper surface,means associated with the said electron gun for concentrating the beamemitted by said electron gun and for causing it to scan the lowersurface of said screen to deposit electric image charges thereon, meansassociated with the said receiving tube for causing said screen tovibrate in a vertical direction at definite time intervals therebyagitating the opaque light sensitive particles causing said particles torebound from the surface of the screen, means associated with thesaidreceiving tube for uniformly lighting and energizing the opaquelight sensitive particles, an electrode parallel tothe upper surface ofsaid screen for collecting photoelectrons emitted by said lightsensitive particles, whereby the said light sensitive particles inrebounding from the upper surface of said screen in an electricallycharged state are electrostatically attracted by the said electric imagecharges on the lower surface of the said screen so as to form on thesaid screen when it ceases to vibrate a semi-opaque image conforming tothe pattern of the said electric image charges.

18. Receiving tube comprising an electron gun emitting an electronicbeam, a first screen of transparent material of low electricalconductivity arranged so as to be exposed to the electrons emitted bythe electron gun, a second screen of conducting material parallel to andin close proximity to the lower surface of the said iirst screen but notexposed to the electronic beam, the said second screen having on itsupper surface a layer of fine opaque particles of light sensitivematerial, means associated with said electron gun for concentrating theelectronic beam emitted by said electron gun and for causing it to scanthe upper surface of said first screen to deposit electric image chargesthereon, means associated with the said receiving tube for vibratingsaid second screen in a vertical direction at definite time intervalsthereby agitating said opaque light sensitive particles causing saidparticles to rebound upward toward the lower surface of said firstscreen, means for uniformly lighting and energizing said opaque lightsensitive particles so that said particles in rebounding from the uppersurface of said second screen are electrostatically attracted by thesaid electric image charges deposited on the said first screen so as toform on the said second screen when it ceases to vibrate a semi-opaqueimage conforming to the pattern of the said electric image charges onthe said iirst screen.

LESTER HE SMITH.

